The long-term goal of Project #4 is to better understand the relationship between the observed concentrations in ambient air and specific sources of airborne PCBs in residential and industrial communities. The central hypothesis is that emissions of airborne PCBs are a function of measureable and quantifiable characteristics of the physical-chemical characteristics of the compounds and exposed environmental surfaces on which the PCBs reside. The Aims focus on identification, characterization and prediction of the magnitude and impact of sources of airborne PCBs: Aim 1: To determine the sources and fate of airborne PCB congeners in the urban/industrial complex of Chicago. We hypothesize that airborne PCBs in Chicago originate from contaminated surfaces throughout the city. We will test our hypotheses by deploying air samplers throughout the City of Chicago and over seasons. Using the measurements, models, and geographic databases, we will determine the relative contribution of Chicago sources toward the annual mass of PCBs deposited in Lake Michigan, distinguish long range versus local sources of airborne PCBs to the region, and determine neighborhoods of elevated risk for high exposure to airborne PCBs. Aim 2: To chapacterize the sources and Aroclor PCBs. We hypothesize that non-Aroclor PCBs have beeN released to the environment for decades and conthnue to be released due to their presence in commercial paint and other buil$ing materials. We wihl test this hypothesis by measuring non-Aroclor PCBs in archival and new samples and by measuring PCBs in c/mmercial paint. Using sediment cores and archived sample extracts, we will ddtermine the chronology of environmental exposure to these compounds and the magnitude of their current emissions. Aim 3: To characterize the emission and fate of airborne PCBs in the Indiana Harbor and Ship Canal (IHSC). We hypothesize that the sediment of the IHSC is a major source of airborne PCB congeners to the community of East Chicago, Indiana. To test our hypotheses, we will measure PCBs in deep sediments of the IHSC. We will calculate the release of PCBs under no-dredging and dredging-conditions, including partial Removal that exposes deep sediments. We will monitor the effect of dredging through local and regional air measurements. As a result of the work described here, Project #4 will promote more scientifically-sound and effective action to reduce human exposure to these potentially harmful compounds.